On the Photoelectron Spectrum of O²

Abstract

The photoelectron spectrum of molecular oxygen has been studied in the range 12-28 eV with the 584 Å and 304 Å He lines, and the O 2 + states have been measured accurately. Due to the high resolution of our apparatus we have been able to observe the A 2 Π u state which has been considered as absent in photoelectron spectroscopy work. Its ionization energy is 17.045 eV. Our result is compared with spectroscopic observations of the second negative band system A 2 Π u → X 2 Π g . The relative intensity of the A 2 Π u state is in good agreement with a recent calculation by Dixon and Hull.